Delegatable in python

delegatable.py

# -*- coding: utf-8 -*-
'''
Convenient classes to enable delegate
..codeauthor Tatsuya Suzuki <[email protected]>
'''
import copy
import logging as log
from typing import Sequence, Any, Dict, Tuple

# def delegatable(cls):
    # def __new__(cls, *args, **kwargs):
        # instance = super().__new__(cls)
        # instance.delegates = {}
        # return instance

    # @property
    # def delegates(self) -> Dict[str, Tuple[str]]:
        # return self._delegates

    # @delegates.setter
    # def delegates(self, delegates: Dict[str, Tuple[str]]) -> Dict[str, Tuple[str]]:
        # self._delegates = delegates
        # return self.delegates

    # def delegate(self, *funcs, to: str) -> Sequence:
        # self.delegates.update({to: funcs})
        # return self.delegates

    # def __getattr__(self, name) -> Any:
        # log.debug(f'delegates={self._delegates}')
        # for to, funcs in self._delegates.items():
            # funcs = (funcs,) if type(funcs) is str else funcs
            # for func in funcs:
                # # Check if func is in any of the delegates
                # if name == func and hasattr(getattr(self, to), func):
                    # # Delegate the call
                    # return getattr(getattr(self, to), func)
        # raise AttributeError(f"'{type(self).__name__}' object has no attribute '{name}'")  # noqa: E501

class MetaDelegatable(type):
    def _get_delegates(cls) -> Dict[str, Tuple[str]]:
        return cls._delegates

    def _set_delegates(cls, delegates: Dict[str, Tuple[str]]) -> Dict[str, Tuple[str]]:
        cls._delegates = delegates
        return cls._delegates

    def delegate(cls, *funcs: Sequence[str], to: str) -> Dict[str, Tuple[str]]:
        cls._delegates.update({to: funcs})
        return cls._delegates

    def __getattr__(self, name) -> Any:
        log.debug(f'delegates={self._delegates}')
        for to, funcs in self._delegates.items():
            funcs = (funcs,) if type(funcs) is str else funcs
            for func in funcs:
                # Check if func is in any of the delegates
                if name == func and hasattr(getattr(self, to), func):
                    # Delegate the call
                    return getattr(getattr(self, to), func)
        raise AttributeError(f"'{type(self).__name__}' object has no attribute '{name}'")  # noqa: E501

    def __prepare__(name, bases, **kwds):
        _dict_ = {}
        _dict_['_delegates'] = {}
        _dict_['delegates'] = property(MetaDelegatable._get_delegates, MetaDelegatable._set_delegates)
        _dict_['delegate'] = classmethod(MetaDelegatable.delegate)
        _dict_['__getattr__'] = MetaDelegatable.__getattr__
        return _dict_


    def __new__(cls, name, bases, attrs):
        attrs['_delegates'] = {}
        attrs['delegates'] = property(cls._get_delegates, cls._set_delegates)
        attrs['delegate'] = cls.delegate
        attrs['__getattr__'] = cls.__getattr__
        instance = super().__new__(cls, name, bases, attrs)
        return instance


class Delegatable:
    def __new__(cls, *args, **kwargs):
        instance = super().__new__(cls)
        instance.delegates = {}
        return instance

    @property
    def delegates(self) -> Dict[str, Tuple[str]]:
        return self._delegates

    @delegates.setter
    def delegates(self, delegates: Dict[str, Tuple[str]]) -> Dict[str, Tuple[str]]:
        self._delegates = delegates
        return self.delegates

    def delegate(self, *funcs, to: str) -> Sequence:
        self.delegates.update({to: funcs})
        return self.delegates

    def __getattr__(self, name) -> Any:
        log.debug(f'delegates={self._delegates}')
        for to, funcs in self._delegates.items():
            funcs = (funcs,) if type(funcs) is str else funcs
            for func in funcs:
                # Check if func is in any of the delegates
                if name == func and hasattr(getattr(self, to), func):
                    # Delegate the call
                    return getattr(getattr(self, to), func)
        raise AttributeError(f"'{type(self).__name__}' object has no attribute '{name}'")  # noqa: E501

delegatable_test.py

# testing_requirements.txt
# ```
# pytest-describe=1.0.0
# ```

# testing_requirements.txt
# ```
# pytest-describe=1.0.0
# ```

import pytest
from chalicelib.core.extension import Delegatable, MetaDelegatable


# @delegatable
# class DecoQueue:
    # def __init__(self, name='default_queue'):
        # self._name = name
        # self.q = []
        # self.s = ','

    # @property
    # def name(self):
        # return self._name


class MetaQueue(metaclass=MetaDelegatable):
    delegate("append", "pop", "copy", to="q")

    def __init__(self, name='default_queue'):
        self._name = name
        self.q = []
        self.s = ','

    @property
    def name(self):
        return self._name


class Parent:
    pass


class Queue(Parent, Delegatable):
    def __init__(self, name='default_queue'):
        self._name = name
        self.q = []

    @property
    def name(self):
        return self._name


def describe_MetaDelegatable():
    def describe_delegate():
        def when_delegated_function_called():
            def it_returns_value_of_the_delegated_function():
                # delegate("append", "pop", "copy", to="q")
                que = MetaQueue('')
                que.append(1)
                que.append(2)
                que.pop(0)
                assert que.q == [2]

        def when_undelegated_function_called():
            def it_deosnt_polute_another_property():
                que = MetaQueue('sub_queue')
                que.delegate("append", "pop", "copy", to="q")
                que.append('a')
                assert que.name == 'sub_queue'

            def it_overwrites_all_delegates():
                que = MetaQueue('sub_queue')
                que.delegate("append", "pop", "copy", to="q")
                que.delegates = {"s": ("join")}
                with pytest.raises(AttributeError) as exc_info:
                    que.append('a')
                assert "'MetaQueue' object has no attribute 'append'" == str(exc_info.value)  # noqa: E501

        def when_undefined_function_called():
            def it_raises_error_when_undefined_attr_is_called():
                with pytest.raises(Exception):
                    MetaQueue('').undefined(1)

    def describe_delegates():
        def when_delegated_function_called():
            def it_sets_delegates():
                que = MetaQueue('')
                que.delegates = {"s": "join"}
                assert que.delegates == {"s": "join"}

            def it_returns_value_of_the_delegated_function():
                que = MetaQueue('')
                que.delegates = {"s": "join"}
                actual = que.join(['a', 'b'])
                assert actual == 'a,b'


def describe_Delegatable():
    def describe_delegate():
        def when_delegated_function_called():
            def it_returns_value_of_the_delegated_function():
                que = Queue('')
                que.delegate("append", "pop", to="q")
                que.append(1)
                que.append(2)
                que.pop(0)
                assert que.q == [2]

        def when_undelegated_function_called():
            def it_deosnt_polute_another_property():
                que = Queue('sub_queue')
                que.delegate("append", "pop", to="q")
                que.append(1)
                assert que.name == 'sub_queue'

        def when_undefined_function_called():
            def it_raises_error_when_undefined_attr_is_called():
                with pytest.raises(Exception):
                    Queue('').undefined(1)

    def describe_delegates():
        def when_delegated_function_called():
            def it_sets_delegates():
                que = MetaQueue('')
                que.delegates = {"s": "join"}
                assert que.delegates == {"s": "join"}

            def it_returns_value_of_the_delegated_function():
                que = MetaQueue('')
                que.delegates = {"s": "join"}
                actual = que.join(['a', 'b'])
                assert actual == 'a,b'